1. Field of the Invention
The present invention relates to alicyclic compounds, and more particularly to dissolution inhibitors used for preparing positive photoresist composition.
2. Description of Related Art
Currently, semiconductor industry trends indicate that the development of high performance logic processors and 1-Gbit DRAM will require the availability of below 0.18 xcexcm lithographic processes. In theory, two methods of forming finer resist patterns are to shorten the wavelength of an exposure light source and increase the numerical aperture (NA) of an exposure system.
Semiconductor industry implemented in manufacture of devices by deep UV lithography employing a KrF excimer laser (248 nm) stepper for 0.25 xcexcm process. Due to the optical enhancement techniques such as high NA optical elements, phase shift mask, etc. The appearance of 248 nm KrF scanner offers the pilot-run of 0.18 xcexcm process and development of below 0.15 xcexcm process. However, there is a limit of wavelength shorten, the more difficult of mask produced. In order to minimize the device size, efforts to develop 193 nm (ArF excimer laser) lithography and resists have been tremendously accelerated in the last several years.
In addition to improved resolution, it is also desirable to provide positive resist materials having improved sensitivity. One approach to improving sensitivity uses the concept of chemical amplification. Chemical amplification involves the photogeneration within the resists of species that catalyze subsequent chemical events. One method of chemical amplification includes dissolution inhibition, wherein a masked phenol or protected carboxylic acid is mixed with a phenolic resin, resulting in a drastic decrease in the dissolution rate of the polymer in aqueous base developing solutions. A photoactivated acid-catalyzed deprotection reaction is then used to free the phenol or the carboxylic acid. As a result, the dissolution inhibitor is converted into a dissolution promoter in the radiation exposed areas of the resist material, allowing for the development of positive images.
There remains a need in the art for a positive photoresist composition having both high resolution and high sensitivity. There also remains a need in the art of composition for positive photoresist, which are useful in deep-UV image resolution techniques. Moreover, there remains a need in the art for positive photoresist dissolution inhibitors capable of providing high sensitivity.
The present invention relates to alicyclic compounds of the formula (1): 
wherein R1 and R2 each independently is a hydroxyl group, a C1-8 hydroxyalkyl group, or a C3-8 hydroxycycloalkyl group; R3, R4 and R5 each independently is a hydrogen, a C1-8 hydroxyalkyl group, a C1-6 carboxylic acid or a C3-8 carboxylic acid ester; k is an integer of 0, 1, 2, 3, 4, 5 or 6.
The alicyclic compounds of the formula (1) can be applied as dissolution inhibitors, for example, 
wherein i is 0 or 1, and the formula (14) is preferred, such as compounds of the following formulas (15), (16), and (17). 
trans-2,3-dihydroxylbicyclo[2.2.1]hepta-2-carboxylic acid tert-butyl ester 
cis-2,3-dihydroxylbicyclo[2.2.1]hepta-2-carboxylic acid tert-butyl ester 
cis-3,4-dihydroxyltetracyclo[4.4.0.12,5.17,10]dodec-8-ene-carboxylic acid tert-butyl ester
The alicyclic compounds of the present invention can be used for preparing photoresist composition which has high transparency to deep UV light and is capable of forming good fine patterns, roughness and high sensitivity, thus being useful as a chemically amplified type resist when exposed to deep UV light from an KrF and ArF excimer laser.
The present invention relates to alicyclic compounds of the formula 
wherein R1 and R2 each independently is a hydroxyl group, a C1-8 hydroxyalkyl group, or a C3-8 hydroxycycloalkyl group; R3, R4 and R5 each independently is a hydrogen, a C1-8 hydroxyalkyl group, a C1-6 carboxylic acid or a C3-8 carboxylic acid ester; k is an integer of 0, 1, 2, 3, 4, 5 or 6, which can be prepared by reacting iso-butyl esteric polycyclic alkene of the formula (1-1) 
with oxidants to form a hydroxyl group, or further reacting with proper chemicals to form an alkyl group. The oxidants are not strictly limited, for example, m-chloroperoxybenzoic acid, or potassium permanganate.
The compounds of formula (1) in the present invention can be applied as dissolution inhibitors to prepare positive photoresist composition with a polymer, a photoactived agent, and an acid quencher.
Suitable polymers for use in the present invention will be known to those skilled in the art. Preferably, the polymers will be transparent in at least a portion of the ultraviolet region of the electromagnetic spectrum. As used herein, the term xe2x80x9ctransparencyxe2x80x9d refers to a 500 xcexcm thickness of polymer which essentially has an optical density of not more then 2.0 xcexcmxe2x88x921 in the wavelengths between about 190 nm and about 440 nm. Preferably, a 500 xcexcm sample of the polymer has an optical density of not more than 2.0 xcexcmxe2x88x921 at one or more of the following wavelengths: 193 nm, 248 nm, 254 nm, and 365 nm.
Polymers which are useful in the present invention are generally soluble in an aqueous base solution after being UV irradiated. Any suitable polymers known to those skilled in the art may be employed in the practice of the present invention. Typically, suitable polymers contain a structure unit represented by the following formula (18), (19) or (20): 
wherein R is a hydrogen or a C1-4 alkyl group; Rxe2x80x2 is a hydrogen or a C1-4 alkyl group.
Preferably, the above polymer is a polymer contains a structure unit selected from the following formula (21) to formula (29), 
in the above structure unit of formula (21), (22), (24), (25), (26), and (29), wherein l+m+n=1, more preferably l/(l+m+n)=0.1-0.5, m/(l+m+n)=0.1-0.5, and n/(l+m+n)=0.1-0.5; in the above structure unit of formula (23), wherein l+m+n+o=1, more preferably l/(l+m+n+o)=0.1-0.5, m/(l+m+n+o)=0.1-0.5, n/(l+m+n+o)=0.1-0.5 and o/(l+m+n+o)=0.1-0.5; in the above structure unit of formula (27) and (28), wherein l+m=1, more preferably l/(l+m)=0.1-0.9, and m/(l+m)=0.1-0.9.
Any suitable photoactived agent known to those skilled in the art may be employed in the practice of the present invention. As used herein, the term xe2x80x9cphotoactived agentxe2x80x9d refers to a compound whose chemical composition is altered upon exposure to radiation. Preferred photoactived agents include photoacid generators. Photoacid generators produce acid upon exposure to radiation. Photoacid generators, which are suitable for the present invention typically, produce strong acid upon exposure to radiation. There is no special limit to photoacid generators here. The photoacid generator suitable for the chemical amplified photoresist composition of the present invention meet the requirement to maintain stability before exposure. Preferably, suitable photoacid generators are: 
The positive photoresist composition of the present invention can further include acid scavengers to adjust the diffusion of acid. Suitable acid scavengers can be 
The ratio of each component of the present invention can be changed in wide a range. In general, the minimum relative weight percentage for each component is 1%, and the maximum relative percentage is 98%. The composition of the present invention preferably contains polymer 10-98% by weight, photoactived agent 1-50% by weight, and dissolution inhibitor 1-50% by weight.
The positive photoresist composition of the present invention can be used to obtain chemical amplified photoresist. The positive photoresist of the present invention can be obtained by simply mixing the components together. There are no limits for the mixing methods. The positive photoresist composition of the present invention can be made by either adding other components into the solution of the photosensitive polymers (or copolymers) or adding the photosensitive polymers (or copolymers) into the solution of other components.
The resolution, shape, roughness and sensitivity of the positive photoresist composition are good, when compounds of the present invention are applied to. In addition, the depth of focus, exposure border and removing border are excellent.